1. Field of the Invention
This invention relates to a graft polymerization preformer, which is useful as adhesive, coating agent, quality improver, microdispersion promoter, polymer alloy former, functional molding material, agent for providing solubility of polymer, etc. and permits a high graft efficiency to be obtained.
2. Prior Art
Heretofore, ethylene (co-and/or) polymers have been used extensively owing to their excellent characters, and also there are attempts to improve their characters and use them in new fields.
For example, low density ethylene polymers have been used as molding material because of their moldability and satisfactory physical and chemical properties of their product.
Also, it has been in practice to mix vinyl polymers, e.g., polystyrene, with low density ethylene polymers as molding material, in order to improve the rigidity, dimensional stability, printing property, etc. of the low density ethylene polymers.
Further, it is well known in the art that epoxy-group-containing olefin copolymers provide satisfactory adhesive force as adhesive to bond together metal and plastic material due to their polarity. Further, since they have elasticity and reactive properties, they are used as condensation polymers; particularly, they are used as impact improving agents by being reacted with engineering plastics.
Further, since the ethylene-(metha-and/or) acrylic ester copolymers and .alpha.-olefin-vinyl ester copolymers have excellent flexibility, weather-proof proper property and shock resistance, they are extensively used as molding material, and .alpha.-olefin-vinyl ester copolymers are also broadly used for hot-melt adhesives. Further, recently there have been attempts to use both copolymers as shock resistance improving agents for engineering plastics.
Further, since ethylene-propylene copolymer rubber and ethylene-propylene-diene copolymer rubber have excellent rubber elasticity, flexibility, coldness-proof property and weather-proof property, they are extensively used as rubber material, and also recently there are attempts to use them as shock resistance improving agents for engineering plastics.
However, since olefin (co-and/or) polymers and vinyl polymers are not satisfactorily soluble to each other, it is not in practice to incorporate more than 10% by weight of vinyl copolymer. Usually, vinyl polymer is incorporated only by 0.2 and 5% by weight. Even where such a small quantity of vinyl copolymer is mixed, the shock resistance of the mixtures is reduced due to the unsatisfactory mutual solubility of the two resins, and also deteriorated appearance is liable to occur.
Further, when ethylene copolymers are used as shock resistance improving agent, sufficient shock resistance improvement effect can not be obtained because of low mutual solubility and dispersion property.
For example, in case of the epoxy-group-containing olefin copolymer, the scope of applications is limited to materials which can react with epoxy group. Therefore, it has been liable that sufficient adhesive force can not be obtained with materials which do not react with epoxy group, e.g., vinyl copolymers or sufficient shock resistance can not be obtained due to low dispersion force with respect to materials.
Therefore, there have been attempts to increase the solubility with engineering plastics.
For example, there have been attempts to increase the solubility with the engineering plastics by increasing the proportion of ethylene-(metha-and/or) acrylic ester copolymers and .alpha.-olefin-vinyl ester copolymer with respect to (metha-and/or) acrylic ester or vinyl ester. Further, it has been attempted to introduce functional groups such as epoxy group, carboxyl group and acid anhydride group for reaction with residual functional groups of engineering plastics, particularly, condensation engineering plastics to increase the solubility and improve the shock resistance improvement effect.
In the meantime, it is well-known in the art that graft copolymers, in which a polymer having a high solubility with other resins and a functional polymer are chemically combined in a molecule, is preferred to improve the solubility with respect to other resins.
Generally, as a method of graft combining a vinyl polymer with olefin (co-and/or) polymer, there has been proposed olefin (co-and/or) polymer, which is obtained by graft polymerizing vinyl monomer, e.g., styrene polymer, with olefin (co-and/or) polymer by irradiation with ionizable radiation. This method provides considerable effects for causing uniform dispersion of vinyl copolymer in olefin (co-and/or) polymer.
As further well-known method, there is a liquid graft polymerization method making use of such solvent as xylene or toluene. Also, there is an emulsification graft polymerization method.
Further, it has been proposed to impregnate olefin (co-and/or) polymer particles with vinyl monomers and cause polymerization of the resultant system using an aqueous suspension (as disclosed in Japanese Patent Publication Sho 58-51010 and Japanese Patent Publication Sho 58-53003. According to this method, in the polymerized resin composition, vinyl polymer is uniformly mixed. With this method, satisfactory results can be obtained in comparison to other methods.
However, the prior art method for causing graft coupling of vinyl polymers to olefin (co-and/or) polymers is not fully satisfactory.
More specifically, the method of irradiation of ionizable radiant rays is based on a special process of a radiation graft polymerization process. Therefore, this method has problems in economy and encounters difficulties in putting it into practice. Further, in this method there is a limitation in the amount of vinyl monomers to be introduced.
Further, in the solution graft polymerization process, polymerization is done in a state in which the system to be graft polymerized is diluted in a large quantity of solvent, from the standpoint of the solubility of the olefin (co-and/or) polymer, there is less opportunity of contact of vinyl monomers, polymerization initiators, and olefin (co-and/or) polymers with one another, and generally the reaction efficiency of vinyl monomers is low. Further, there are complicated after-treatment steps, which is economically disadvantageous. Further, there is an emulsified graft polymerization process. In this case, the reaction is limited only to the on-surface reactions of olefin (co-and/or) polymer particles.
In the process of polymerization in a water suspension, the graft efficiency of the resin composition obtained by this process is low. Therefore, vinyl polymer particles which have been uniformly dispersed at the end of the completion of polymerization, are liable to be aggregated secondarily due to heating in the secondary processing or contact with the solvent, thus giving rise to problems when using the obtained resin composition as microdispersion promoters, compatibilizers of polymer alloy and agents for providing polymer solubility.